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 Enquiries SEED News - mar/apr 2005
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This section is coordinated by the professors from the Federal University of Pelotas-Brazil, with the objective of answering the inquiries sent by the readers.
Send your question to e-mail: silmar@seednews.inf.br
I received a lot of genetic rice seeds, in which about 2% of the seeds were peeled. I would like to ask if it is possible to protect them through a treatment with fungicide.
In the seed harvesting process, it is normal that some get peeled, however, during seed conditioning they are removed by the air screen cleaner and the gravity table. In your case, the work was not well done. Thereby, you had an inconvenience, because in spite of the fungicide protecting the seeds, it doesn't have effect in seeds that are dead. The storage potential of rice seeds that are peeled and without protection, is less than a week.
I liked the main article of SEED News from the last edition. In fact, sampling is very important to determine the quality of a seed lot, where few seeds represent many. I am in doubt about the submitted sample, could you explain it?
A seed lot can have several tons and to determine its quality random samples are taken. Basically there are four types of samples; the primaries are taken from several places of the seed lot; the composed sample is the gathering of all primary samples; the submitted is the composed sample homogenized and divided, and for cereals crops, in general, is a kilogram that is sent for the seed laboratory; and the working sample is the division of the submitted sample used by the laboratory to accomplish evaluations.
I have been observing that in the process of accrediting laboratories for analyzing GMO materials the criteria used is based on performance; I have certain difficulty of understanding it, since I thought that all the laboratories used the same tests. Could you explain this?
During evaluation, if a seed lot contains GMO material, several tests can be used, some of them use the physiological performance of the seeds and others use molecular techniques. To certify that the laboratory is evaluating the seed lot appropriately, the certifier prepares samples with different contaminations and sends them to the laboratory for determination and independently of the methods that are used, getting the right determination it will be accredited. Therefore, the accreditation of the laboratory is based on its performance not in the capacity to follow an universal protocol.
In the seed cleaning process I observe that the screens were with many obstructed holes, how can I verify if the rubber balls that are below of the screens with the purpose of unblocking them are working well?
The screens should work with their perforations opened and one of the mechanisms used to accomplish, is to use rubber balls below the screens, that while jumping unblock the holes. After some time, the balls start losing elasticity jumping less and less, therefore, when a rubber ball is released from a meter height, it should return at least 70 cm to still be considered capable to unblock the holes of the screens.
The company that I work for, decided to buy two continuous flow dryers for soybean seeds. I was consulting the catalog that came with the dryers and I could not find recommendations for the drying process. I would like to know which are the main controls that should be followed are.
The main control is the temperature of the drying air: it should be such that the temperature of the soybean seed should not be over 40°C.To accomplish it, a seed sample from the hottest place of the dryer must be taken and placed in a container with a thermometer for five minutes before reading. Usually, the temperature of the drying air is 20°C superior in relation to the seed, however it varies depending on the dryer model.
Another control is the determination of seed moisture content of seeds coming out from the dryer, because in case they are with more than 13% moisture they must go once again through the dryer.
To adjust the temperature of the drying air and the time that seeds go by the dryer requests some practice, which is obtained after some drying loads.
I am having difficulties in buying forages seeds with purity above 98%, Is it possible to use machines to clean them?
Forages seeds, especially the chaffy ones, as ryegrass, andropogon and brachiaria, are a little hard to clean, however the seed producer that owns a seed conditioning plant with the main machines (air screen cleaner, gravity table, cylinder separator, debearder) and a good set of screens will not have difficulties in cleaning their seeds. We would like to emphasize that there are situations in which the seed is offered with low purity to reduce the price.
I am working with a variety of soybean seed whose format of the seeds is far from round and every time that I pass them through the spiral separator, the loss of good seeds is high, what can I do?
Indeed the loss of seeds in the spiral separator can be high for egg shaped seeds. To avoid that loss, spirals with smaller diameter should be used or in case that spirals have speed reducers fingers, they should be removed. Another alternative is not to bypass the seeds from the spiral, separating the deformed seeds only in the gravity table. It is good to remind that the gravity table does not remove cowpea seeds from soybean seeds, which the spiral does.
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